Special Note
Ask an Astrobiologist has received nearly a thousand questions about Nibiru and 2012, with more than 200 answers posted. Please read a summary of the answers that have already been posted, use the search feature and read the FAQ’s before submitting questions on these topics.
-
Question
What is the most widely accepted theory on how photosynthesis evolved from non-photosynthesis based life?
According to NAI's expert at Arizona State University, no widely accepted theory exists so far. A popular one is that it could have evolved from phototaxis, or movement toward light or energy, in hot vent communities (using the black body radiation to find the vent). Chemo-osmotic coupling using respiration (with acceptors other than O2) seems to be older than photosynthesis, and it seems the same is true for autotrophy/CO2 fixation. To get photosynthesis, the organism would have needed only to couple the energy of incoming photons to the formation of the proton gradient which is the energy source for making ATP, the cellular energy currency. All the other cellular machinery was already in place (CO2 fixation, making ATP from proton gradients). It seems possible that the system - light energy triggering the passing of electrons from an energized pigment molecule to an acceptor - was first used as a sensing mechanism, and subsequently incorporated into a single photosystem cyclic electron transport scheme (like in Rhodospirillum). Later, linear electron transport along a membrane, systems to interface with electron donors, and the addition of a second photosystem responsive to a different wavelength of light evolved. While there are reasonable scenarios for the latter steps, the first remain rather murky.
May 1, 2002
- How frequently are questions answered?
- I asked a question but there was no answer?
- Who is the Astrobiologist answering these questions?
- Will I get an email when my question is answered?
- What college courses should I take to become an astrobiologist?
- How can I get a job as an astrobiologist at NASA?
- Have aliens visited Earth? Are UFOs real?
- Is there a planet or brown dwarf called Nibiru or Eris that is approaching the Earth and threatening our planet with widespread destruction?
- Is it true that the Sun will be in the center of the Milky Way Galaxy in December 2012 and that this will cause a pole shift and massive destruction.
- Has NASA discovered life on other worlds?
- Astrobiology Career Path Suggestions